In vitro characterization and micromechanics of tumor cell chemotactic protrusion, locomotion, and extravasation.

The objective of this paper is to introduce some novel in vitro applications in characterizing human melanoma cell protrusion and migration in response to soluble extracellular matrix protein stimulation. Specifically, we describe two assay systems: (1) dual-micropipette manipulation and (2) flow-migration chamber. Applications of the dual-micropipet technique provided kinetic measure of cell movement, cyclic pseudopod protrusion, and subsequent cell locomotion governed by chemotactic molecular transport dynamics. Chemotactic concentration gradient was found to influence significantly pseudopod protrusion frequency and locomotion speed, but not the protrusion extension. To further characterize active tumor cell extravasation, a process that involves dynamic tumor cell adhesion to vascular endothelium under flow conditions and subsequent transendothelial migration in response to chemotactic signals from the interstitial space, we developed a flow-migration chemotaxis system. This assay enabled characterization of tumor cell transcellular migration in terms of chemotactic signal gradients, shear forces, and cell-substrate adhesion. Results suggest that shear flow plays significant roles in tumor cell extravasation that is regulated by both tumor cell motility and tumor cell adhesion to endothelial molecules in a cooperative process.